Electronic alternating voltage regulator



July 31, 1951 J. SCHULTZ ELECTRONIC ALTERNATING VOLTAGE REGULATOR F'il ed April 28, 1948 3 Rseuurso OUTPUT VOLTAGE Inventor: Jack Lfichults, M

HisAttoPney Patented July 31, 1951 ELECTRONIC ALTERNATING VOLTAGE REGULATOR Jack L. Schultz, Syracuse, N. Y., asslgnor to General Electric Company, a corporation of New York Application April 28, 1948, Serial No. 23,803

1 Claim.

output is substantially unaflected by frequency over a wide range of frequency variations.

For additional objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawing, and also .to the appended claim in which the features of the invention believed to be novel are particularly 7 pointed out.

In the drawings:

Fig. 1 is a circuit diagram of an alternating voltage regulator embodying the invention; and

Fig. 2 is a circuit diagram of a portion of Fig. 1, within the dashed rectangle A, showing the same circuit elements rearranged in the form of a bridge network to facilitate analysis of the operation of the invention.

In Fig. l unregulated alternating voltage is supplied to the regulator input terminals l and 2 from any suitable source (not shown). Terminals 3 and 4 are the output terminals from which the regulated voltage is supplied to any suitable load device (also not shown). -A transformer It has a primary 5 inserted in series in the line be tween terminals 2 and 4. One terminal iii, of its secondary winding 6 is connected directly to the anode and screen grid of a valve H and to the cathodeof a valve 21. The other terminal I1 is connected directly to the anode and screen rid of valve 2| and to the cathode of valve H. A pair of resistors l2 and 22 are serially connected between the cathodes of valves II and 2|. The control grid and cathode of valve I l are connected together through a resistor l4 and shunt by-pass capacitor 13; and the control grid and cathode of valve 2i are similarly connected together through a resistor 24 and shunt by-pass capacitor 23. The control grids of the two valves are also connected together through resistors l5 and 25 in series.

As is best illustrated inFlg. 2, resistors l2 and 22 each constitute an arm of a bridge across the terminals of secondary winding 5, while resistors l4-|5 in series and 2425 in series constitute the other two arms.

A source of filtered unidirectional voltage, of magnitude proportional to the magnitude of the regulated alternating output voltage, is provided by. means of ,a, rectifier system comprising a transformer 52, a full wave rectifier valve 5| and a filter network comprising a resistor 53 and condenser 54.

A resistor 42, in series with a gaseous electronic discharge device (I which has a substantially constant voltage drop thereacross when in a continuously conducting state, is connected in parallel with filter capacitor 54. The voltage drop across the gaseous discharge device 4| provides a constant reference voltage in the operation of the circuit. A potentiometer resistor 44 is also connected in parallel with capacitor 54 and part of the voltage across it is tapped at an adjustable point 45 to provide another reference voltage, varying in magnitude with the regulated alternating output voltage.

A pentode valve 3|, serving as an amplifying device, has its anode connected, by means of a.

conductor 8, to the lowerpoint of the bridge formed by the junction of resistors l5 and 25. Its cathode and suppressor grid are connected to thesource of constant unidirectional voltage provided by the junction of resistor 42 and gaseous discharge valve 4|. Its control grid is connected to the source of variable reference voltage provided by the tap 45 on resistor 44. Any alternating component of the grid voltage is bypassed by means of capacitor 32. A voltage dropping and filtering network, consisting of resistors 34 and 35 and capacitor 33 supplies operating potential to the screen grid of valve 3|. The upper point of the bridge formed by the junction of resistors I2 and 22 is connected by means of conductor 1 to the positive terminal of the unidirectional voltage supply, at the junction of re sistor 53 and filtering capacitor 54.

In operation, the load current flowing through primary winding 5 of the line transformer l0 induces an alternating voltage in secondary winding 5. The valves II and 2! are cross-connected to conduct in opposite directions and the grid bias voltages on these valves control the secondary current. A more negative bias on either valve will reduce. the alternating current in the secondary 6 and will raise the voltage drop across the control valves and secondary winding 5. This in turn will correspondingly raise the drop across the primary winding 5 in series with the line and thus decrease the regulated alternating output voltage. Another method oi visualizing the operation is to conceive of the line transformer as reflecting into the line a bidirectional impedance comprising alternately the anode-to-cathode impedance of each control valve, on respective half cycles, the reflected impedance being controlled by the grid bias voltages on these valves, and by this means regulating the output voltage.

The control grid bias applied to valves II and 2| is provided as follows. The unidirectional voltage existing across capacitor '54 through the operation of transformer 52, full wave rectifier valve and filtering resistor 53 is proportional to the regulated alternating output voltage. Due to the constant voltage characteristic of gaseous discharge valve 4|, the voltage across it'will remain substantially constant, independently of the voltage across capacitor 54. The voltage across resistor 44 will be directly proportional to the regulated alternating output voltage and so, also, will be that existing at tap 45 and applied directly to the control grid of amplifying valve 3|.

Tap 45 is initially adjusted so that with normal alternating input and output voltages, the potential at the tap is equal to that across gaseous discharge valve 4|. An increase in the line alternating input voltage will cause the regulated alternating output voltage to tend towards an equal increase in the same direction. However, the first initial increase of the regulated alternating output voltage will cause the unidirectional potential at tap 45 to increase proportionally in a positive direction. and consequently to increase the anode current flowing through valve 3|. This in turn will increase the current through the bridge and consequently the increased voltage drops across resistors I4 and 24 will place greater negative bias voltages on the control grids of valves II and 2|. As previously mentioned, this will reflect a higher impedance into winding 5 of the line transformer, and-tend to reduce the regulated alternating output voltage. Accordingly, the regulated alternating output voltage will only vary a very small amount in the direction of the input voltage change. This amount can be made as small as desired by proper design of the transformer 52, the line transformer 5-5, and the gain of the amplifying device 3|.

It will be noted that, whereas a large alternating voltage appears between the cathodes and anodes of both valves and 2 I, nevertheless, due

to the balancing action of the bridge and the shunting capacitors l3 and 23, only a small ripple voltage appears between the respective grids and cathodes of the control valves. Also due to the bridge arrangement equal control biases appear on the respective grids of H and 2| which remain constant at every part of the alternating voltage cycle.

Merely by way of illustration, in one particular embodiment of my invention the following circuit constants have been used:

Control valves H and 2| Type 6L6 Amplifying valve 3| Type 6837 Gaseous discharge valve 4| Type VR-150 Full wave rectifier valve 5|---" Type 6X5 Resistors I2 and 22 50,000 ohms Resistors l4, I5, 24 and 25 100,000 ohms Resistors 34 and 35 200,000 ohms Resistor 42 30,000 ohms Resistor ll 300,000 ohms Resistor 53 2,000 ohms Capacitors I3 and 23 1 microfarad Capacitor 32-. .01 microfarad Capacitor 33 .5 microfarad Capacitors l3 and 54 2 microfarads In the particular system using the above circuit constants, the regulator circuit was designed to maintain a constant voltage of 115 volts across a 300-watt load, over a frequency range extending from 60 to 3,000 cycles per second. At zero bias on valves II and 2|, the voltage drop across the control valves l I and 2| was 300 volts R. M. $4

which corresponded to a primary voltage drop of 8 volts R. M. S. With the bias voltage across the control valves at its maximum negative value,

the voltage across these valves reached 1200 volts R. M. S. and the primary voltage drop was then 24 volts R. M. S. Under these conditions the circuit could be made to regulate the output voltage at volts R. M. S. for an input voltage range of 123 to 139 volts. Using a voltage transformer 52 such that the rectified voltage across capacitor 54 was 400 volts D.-C., an increase in input voltage from 123 to 139 volts R. M. S. resulted in an increase in output voltage only from 115.0 volts R. M. S. to 115.2 volts R. M. S.

The change in regulated output voltage resulting from change in frequency will depend upon the design of transformer 52 and of the rectifier and filter circuit 5|, 53 and II. This change can be made as small as desired.

While a specific embodiment has been shown and described, it will, of course, be understood that various modifications may be made. without departing from the invention. To mention but a few, different types of valves or rectifying, filtering and amplifying circuits may be employed. Also, if the line currents are sufilciently small,

transformer 5-6 may be dispensed with altogether and the line connected directly through the bridge circuit. The appended claim is therefore intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

The combination, in an alternating voltage regulator. system having input and output terminals and means for developing a unidirectional control voltage continuously proportional to the alternating voltage at said output terminals, of a transformer having primary and secondary windings, said primary winding being connected in series circuit between said input and output terminals, means for providing a unidirectional substantially constant reference voltage, means for amplifying the difference between said control and reference voltages, a bridge circuit comprising four impedance arms capable of carrying direct current between first and second pairs of conjugate points, said secondary winding being connected between said first pair of conjugate points, and said amplified difference voltage being applied across said second pair of conjugate points, and a pair of grid-controlled electron discharge devices having their anode-to-cathode paths reversely connected in parallel between said first pair of points, the control grids of said electron discharge devices being connected to taps on bridge arms adjacent to their respective cathode connections to said first pair of points whereby the impedance presented by said electron discharge devices to the secondary of said transformer may be caused to vary in accordance with said amplified difierence voltage to maintain the alternating voltage at said output terminal substantially constant.

JACK L. SCHULTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,571,304 Sindeband Feb. 2, 1926 2,302,889 Reed Nov. 24, 1942 2,392,434 Trucksess Jan. 8, 1946 

